A conventional pressure-operated valve is disclosed in, for example, JP, A, 2006-77823 (Patent Document 1), and JP, A, 2002-71037 (Patent Document 2).
The valve disclosed in Patent Document 1 is a valve in which an inner space is formed by a cap member having an inlet connection pipe and an outlet connection pipe and by a stopper member having a through hole in the center thereof, the inner space is separated to a first room and a second room by a diaphragm, and the diaphragm faces a valve seat attached to the outlet connection pipe. Then, when a pressure of the first room is less than a specific value, the diaphragm abuts on the valve seat to close the valve, and when the pressure in the first room is more than a specific value, the diaphragm is removed from the valve seat to open the valve.
The valve disclosed in Patent Document 2 is a relief valve for use in such as a high pressure control valve, in which a reverse plate assembly (diaphragm) and a stopper holding member are swaged to be fixed to a valve housing having an inlet coupling and an outlet coupling, and this reverse plate assembly faces a relief valve port of the valve seat. Then, when a pressure of a valve chamber is less than a specific value, the reverse plate assembly closes the relief valve port, and when the pressure in the valve chamber is more than a specific value, the reverse plate assembly is reversed to open the relief valve port.
This kind of pressure-operated control valve works when a pressure is more than a setup pressure value, and is used instead of, for example, a relief valve disclosed in JP, A, 2003-336914 (Patent Document 3) and a liquid sealing prevention path disclosed in JP, A, 2003-139429 (Patent Document 4). Therefore, in many cases, the valve is used for a security purpose, and required to have a small leak, because under the setup pressure, even a tiny valve leak directly reduces a cycle COP value.